This invention relates to a suspension system incorporating torque rods that define a parallelogram; one of the torque rods and a like torque rod on the opposite side of the vehicle defines an A-frame configuration; these torque rods are independently supported from the frame to provide stabilization of pitch as well as lateral stabilization while retaining independence of the suspension systems.
Various parallelogram suspension systems are known. U.S. Pat. Nos. 4,132,432 and 4,529,224 to Raidel, represent examples of such parallelograms. Raidel U.S. Pat. No. 4,500,112 also indicates that parallelograms having longitudinally offset pivot points are known and Raidel U.S. Pat. No. 4,181,323 indicates that a parallelogram having a lower torque beam that is bowed is known.
A suspension system having a parallelogram wherein the upper component is a torque rod and an A-frame configuration is disclosed in U.S. Pat. No. 4,773,670, filed Feb. 6, 1987 by John E. Raidel II. In that suspension system, the A-frame is a unitized member having torque rods joined at their inner ends and extending outwardly to the opposite sides of the vehicle. In this arrangement, the operation of the suspension system on one side of the vehicle affects the suspension system on the opposite side of the vehicle
The present invention is particularly suitable for a steer axle for a trailer. The invention incorporates the advantages of the foregoing prior art patents, but provides a suspension system with a parallelogram and A-frame configuration that is independent of the suspension system on the opposite side of the vehicle.